View source for Helsinki Apertium Workshop/Session 0

==Problems in machine translation==

===Analysis===

<center>'''Form does not entirely determine content.'''</center>

This is also called the problem of ambiguity. The problem is that many sentences in natural language can have more than one interpretation, and these interpretations may be translated differently in different languages. Consider the following example: 

:EXEMPLE 3
:'''Здесь нужен пример синтаксической неоднозначности на русском или на чувашском языке (чем проще, тем лучше)'''
:Вот друг Саша, которого я вчера встретил.

===Synthesis===
<center>'''Content does not entirely determine form.''' </center>
This is the problem that in a given language there is usually more than one way to communicate the same meaning for any given meaning. 

:Эсир мӗнле пурӑнатӑр?
:Мӗнле пурнӑҫсем?
:Мӗнле халсем?
:Мӗнле еҫсем?

All of these questions demand the same answer (how are you), but they may be more or less frequently used, or emphasise different things. 

In Apertium, for a given input sentence, one output sentence is produced. It is up to the designer of the translation system to choose which translation they want the system to produce. Often we recommend the most literal translation possible, as this reduces the necessity of transfer rules.

===Transfer===
<center>'''The same content is represented differently in different languages. '''</center>

Languages have different ways of expressing the same meaning. These ways are often incompatible between languages. Consider the following examples expressing the same content: 

:EXEMPLE 5

:''Minä pidän uimisesta''

In Apertium, rules are applied which convert source language structure to target language structure using sequences of lexical forms as an intermediate representation. For further information see: Session 5: Structural transfer basics.

===Description===

<center>'''Representing knowledge about the translation process in machine-readable form.'''</center>

The final problem is that of description. In order to build a machine translation system it is necessary for people with knowledge of both languages to sit down and codify that knowledge in a form explicit and declarative enough for the machine to be able to process it.

While translation is often an unconscious process, we translate without reflecting on the rules that we use to translate, the machine does not have this unconsciousness, and must be told exactly what operations to perform. If these operations rely on information that the machine does not have, or cannot have, then a machine translation will not be possible.

But for many sentences, this information is not necessary:

:EXEMPLE 6